Al $x$ Ga 1–x N/GaN MISHEMTs With a Common Gold-Free Metal-Stack for Source/Drain/Gate

A low-temperature fabrication of Al $x$ Ga 1–x N/GaN MISHEMTs on a 200-mm GaN-on-Si substrate using a common metal stack (Ti/Al/NiV) for concurrent source, drain, and gate formation is demonstrated. An ohmic contact resistance of 0.8 $\Omega $ -mm and a specific contact resistivity of $6\times 10^{\mathrm {-6}} \Omega $ -cm 2 are achieved at an annealing temperature of 500 °C. The fabricated MISHEMTs have excellent electrical characteristics: an $I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}$ ratio of nine decades (due to subnanoampere off -state leakage current up to a −15 V gate bias), and a subthreshold swing of 80 mV/decade (by virtue of a relatively low Al 0.23 Ga 0.77 N/GaN interface-trap density on the order of $10^{11}$ cm $^{\mathrm {-2}}$ eV $^{\mathrm {-1}}$ ). The demonstrated approach is thus a promising alternative toward the gold-free GaN-on-Si integration.